The present invention relates to a map plate for adjusting the angle of elevation of a signal receiving antenna to the direction of an artificial satellite.
When a radiated electromagnetic wave of an artificial satellite is received on the ground, it is necessary to use an antenna of very high gain.
In order to have the direction of the pattern of such an antenna aimed directly at the satellite, it is necessary to carry out very careful scanning in the horizontal and vertical directions and set the antenna in such a position as to obtain the maximum signal receiving level.
Two dimensional scanning is extremely difficult. In order to overcome these difficulties, various types of automatic tracking systems have been specially developed for large scale receiving group stations.
Such a large scale tracking system, however, is not applicable for economic reasons in cases where an electromagnetic wave sent from a satellite is received by a terminal station of a CATV communication system or directly by an individual household or the like in a small scale system.
In consequence, a simple and economical system for adjusting the direction of an antenna is required.
When a signal receiving point on the ground is designated, it is possible to accurately calculate its angle of elevation to such a stationary satellite. If the angle of elevation of the antenna can be preset by a simple method with an error not in excess of the main beam angle of the antenna, then it is considered that the reception of the electromagnetic wave of the satellite will be assured by adjusting the horizontal angle of the antenna so as to obtain the maximum receiving level.
Therefore it is equally possible to get the direction of the antenna to coincide with the direction of the satellite with perfect accuracy by first scanning the horizontal angle to find the direction of maximum reception and then by adjusting the angle of elevation.
In this way, the systematic adjustment of the antenna may be done quickly and easily.
Since the receiving antenna used in the present case is a parabolic antenna with a diameter of about 0.6-4 m, the range of tolerable error of the preset angle becomes approximately .+-.0.3.degree. in cases where the highest frequency band of 12 GHz alloted to satellite communication is used.
We will propose a simple map plate for adjusting the angle of elevation of an antenna so as to direct it correctly at a satellite with an error within the afore-mentioned permissible range. The map plate of the present invention is suitable for use by a simple signal receiving system of an artifical satellite communication system.